[IPV6]: Track device renames in snmp6.

When network device's are renamed, the IPV6 snmp6 code
gets confused. It doesn't track name changes so it will OOPS
when network device's are removed.

The fix is trivial, just unregister/re-register in notify handler.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index e04e493..3452433 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2359,8 +2359,9 @@
 		break;
 
 	case NETDEV_CHANGENAME:
-#ifdef CONFIG_SYSCTL
 		if (idev) {
+			snmp6_unregister_dev(idev);
+#ifdef CONFIG_SYSCTL
 			addrconf_sysctl_unregister(&idev->cnf);
 			neigh_sysctl_unregister(idev->nd_parms);
 			neigh_sysctl_register(dev, idev->nd_parms,
@@ -2368,8 +2369,9 @@
 					      &ndisc_ifinfo_sysctl_change,
 					      NULL);
 			addrconf_sysctl_register(idev, &idev->cnf);
-		}
 #endif
+			snmp6_register_dev(idev);
+		}
 		break;
 	}
 

net/ipv6/proc.c

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index acb306a..920dc9c 100644
--- a/net/ipv6/proc.c
+++ b/net/ipv6/proc.c
@@ -223,6 +223,7 @@
 		return -EINVAL;
 	remove_proc_entry(idev->stats.proc_dir_entry->name,
 			  proc_net_devsnmp6);
+	idev->stats.proc_dir_entry = NULL;
 	return 0;
 }